Fat Loss & Metabolism

Tirzepatide

Mounjaro · Zepbound · dual GLP-1/GIP agonist

FDA-approvedmainstreamsubQ injection

What it is

Tirzepatide is the second-generation GLP-1 agonist from Eli Lilly — FDA-approved as Mounjaro for type 2 diabetes (2022) and as Zepbound for chronic weight management (2023). Unlike Semaglutide which only hits the GLP-1 receptor, Tirzepatide is a dual agonist: it activates both GLP-1 and GIP receptors. The result is more weight loss with similar tolerability.

How it works

The two receptor activation does separate things. GLP-1 handles appetite suppression, slower stomach emptying, and improved insulin sensitivity. GIP further improves insulin response, may amplify fat oxidation, and seems to actually reduce some of the GI side effects of GLP-1 alone. The combination outperforms semaglutide in head-to-head trials.

Benefits

Largest non-investigational weight loss available — up to ~22% body weight at 72 weeks (15 mg dose)
Superior glucose control vs. Semaglutide
Reduced cardiovascular risk markers
Lower blood pressure and improved lipids
Reduced "food noise" and addictive eating
Liver fat reduction

Timeline

Week 1–4: Strong appetite suppression begins. Common nausea during titration.
Week 8–12: 5–10% body weight loss; reduced food cravings.
Week 24: 15–18% body weight loss at higher doses.
Week 72: Peak weight loss (~22% at max dose).

Dosing & titration

Starting dose2.5 mg subQ once weekly (4 weeks)

Standard titration2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg, every 4 weeks if tolerated

Max dose15 mg/week (Zepbound label)

When to titrate upOnly after 4 weeks at current dose with tolerable nausea. Many users get good results at 5–10 mg without going to max.

Side effects & risks

Nausea (most common, especially during titration)
Vomiting, diarrhea, constipation
Acid reflux
Decreased appetite (often desired)
Hair shedding (months 3–6, usually temporary)
Significant muscle loss without protein and resistance training
Gallstones from rapid weight loss
Rare: pancreatitis

Same warnings as Semaglutide: 1g protein/lb bodyweight + lifting is non-negotiable. Black-box warning for medullary thyroid cancer in animals; contraindicated in MEN-2.

Typical price

$300–$1,200/moCompounded tirzepatide: $300–$500/mo. Branded Mounjaro/Zepbound retail ~$1,000–$1,300/mo without insurance.

Studies

Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1) — 22.5% weight loss at 72 weeks. NEJMNew England Journal of Medicine, 2022
Frías JP et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2) — Head-to-head superiority over semaglutide. NEJMNEJM, 2021
Search PubMed for tirzepatide trials — PubMed searchLive PubMed search

Educational reference only. Not medical advice. FDA-approved; requires prescription.